The long term objectives of the present project are to investigate the physiological importance of PGE2 as a negative modulator of phasic glucose-indeed insulin secretion and to elucidate the mechanism of POE's inhibitory actions on beta cell function. The specific aims of the investigation are (1) to examine eicosanoid production in HIT cells and in islets isolated form Syrian hamsters and humans; (2) to determine whether cyclooxygenase and lipoxygenase inhibitors positively and negatively modulate, respectively, insulin release; (3) to assess whether Gi an important mediator of PGE2 action on insulin secretion by determining whether pertussis toxin and anti-Gi antibodies prevent the effects of PGE2 on hormone release; and (4) to determine whether PGE2 has inhibitory effects on insulin secretion that are mediated by non-Gi mechanisms. In this project we will define the role of endogenous PGE2 in insulin release by examining eicosanoid synthesis using HPLC. Perfusion experiments will be performed to determine whether pertussis toxin, an agent that blocks signal transduction by Gi through irreversible ADP-ribosylation, prevents the inhibitory effects of PGE2. Because we have found pertussis toxin to be only partially effective in preventing PGE2 inhibition in the HIT cell, Western analyses of membranes will be performed with anti-Gi antisera to monitor whether pre-treatment with pertussis toxin leads to complete ADP-ribosylation of Gi. The anti-Gi antisera will also be used to determine whether PGE2 mediates all of its inhibitory effects through this G-protein. In our final experiments, we will investigate whether PGE2 has effects on insulin secretion that are independent of adenylate cyclase.